The NWA designation may be available now to a new operator that just isn’t in the system yet. With a T at the end of the flight number meaning this one is a Test flight for someone. Keep an eye on it, soon you may see a P at the end of the flight number meaning a Proving flight, then it’s close to going into service.
In all of my years of flight tracking, I have yet to see an airline use T or P for a test flight or a positioning flight. Most airlines use a specific range of flight numbers for test and positioning (i.e. ferry or deadhead) flights. These flight numbers are 4 digits long and quite often begin with 9.
I have the feeling that the reuse of a designator isn’t done for several years after the designation is no longer in use.